Our objective is to study structural and functional properties of acetylcholin-esterase (AcChE), acetylcholine receptor (AcChR) and other identifiable excitable membrance components and to investigate their interactions with and roles in the excitable membrane. Structural distinctions between various forms of eel AcChE isolated by affinity chromatography will be studied by SDS gel electrophoresis. Antibodies to AcChE subunit components will be investigated. Binding studies of cholinergic ligands, neurotoxins, and Ca ions to purified soluble AcChR are planned, and the essential nature of a free sulfhydryl near the AcChR active site prior to disulfide reduction will be analyzed. The synthesis and interaction of fluorescent probes specific to AcChE or AcChR will be investigated. Membrane fragments rich in AcChE and/or AcChR will be isolated by affinity chromatography, and the accessibility of both proteins when membrane bound will be determined by lactoperoxidase iodination studies. These investigations will permit experimental examination of several proposals in an integral model of nerve excitability. BIBLIOGRAPHIC REFERENCES: Rosenberry T.L.: Catalysis by acetylcholinesterase. Evidence that the rate-limiting step for acylation with certain substrates precedes general acid-base catalysis. Proc. Nat. Acad. Sci. U.S. 72: 3834-3838, 1975. Rosenberry, T.L.: Acetylcholinesterase. In: "The Enzymes of Biological Membranes" (A. Martinosi, ed.), Vol. 4, pp. 331-363, Plenum Press, New York, 1976.